Grinding machine



K. MIDDELBOE GRINDING MACHINE Filed March 8, 192] Saved Wm Patented duly l, 1924..

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KRIS'IIAN MIDDELBOE, 0F FREDERIKSBERG, NEAR COPENHAGEN, DENMARK, AS-

SIGNOR T0 F. L. SMID'IH & (30., OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

GRINDING MACHINE.

Application filed March 8, 1921. Serial No. 450,533.

To all whom it may concern.

Be it known that I, KRIsTIAN Mrnnnneon, a subject of the King of Denmark, residing at 14.- Thorvaldsensvej, Frederiksberg, near Copenhagen, l )enmark, have invented certain new and useful Improvements in Grinding Machines, of which the following is a specification, reference being had to the accompanying drawings, forming a part hereof.

In Letters Patent of the United States No. 1,380,112, dated May'31, 1921, there is shown and described a grinding machine in which the grinding bodies revolve about a vertical axis, between an outer grinding ring and an inner, sectional grinding ring, each section of the inner. grinding ring being urged outwardly, in operation, by the centrifugal action of loading blocks or carriers which have considerable mass and are guided radially upon the supporting disk. In that machine the grinding bodies are shown as spheres and the leading end of each section of the inner grinding ring is made yielding so as to reduce the shocks as the grinding bodies roll from each preceding section into contact with each succeeding section. By the present invention it is sought to improve the construction of such grinding machines so as to provide a greater grinding surface, as by the substitution of cylindrical grinding bodies for spherical grinding bodies, to reduce further the shocks as the grinding bodies roll from one section to another, to provide means whereby the cylindrical grinding bodies shall be retained always with their axes at least nearly parallel with the vertical axis of the machine, and to provide additional means to reduce still further any tendency of the cylindrical grinding bodies to assume positions other than with their axes parallel with the axis of the machine. The invention will be more fully explained hereinafter with reference to the accompanying drawing in which it is illustrated and in which Figure 1 is a view in vertical section, in the plane of the operating shaft, of the improved machine. I

Figure 2 is a partialview of the same in horizontal section on the plane indicated by the broken line 2- 2 of Figure 1.

Figure 3 is a view partly in elevation and partly diagrammatic illustrating the relation of one of the grinding bodies to the outer grinding ring and the guiding device.

In the construction shown the vertical operating shaft a, driven by any convenient means, has secured thereto upper and lower disks 3) and Z) which have on their proximate faces radial ribs 500 to guide the loading blocks or carriers 7' which are received between the disks. Each carrier f supports a corresponding section 0 of the inner grinding ring. In the construction show-n in the application above mentioned, each section of the grinding ring was supported directly on the face of the carrier or loading block and the leading end of each section was made yielding or resilient by cutting away the inner surface of the section so as to leave a space between it and the carrier, the working face of the ring thus being made yielding at its leading end or portion but rigidly supported at its rearward portion. In the present instance each section of the inner grinding ring is supported by the carrier block f so that is shall be yielding or resilient, in a horizontal plane, throughout its length, the section preferably being held at the same time against movement in a vertical direction. This desired result is most conveniently effected by securing each section to its corresponding carrier block by an S-shaped spring r, of relatively broad but thin metal, fastened at its ends, as by bolts 8, to the carrier block and the ring section respectively.

Each grinding body 0, instead of being spherical, as in the machine referred to, is now cylindrical, having an upper portion e and a lower portion 6 separated by a circumferential groove or channel 0 Each grinding body obviously might be formed with all its parts integral or with its members c and c of full diameter, connected by a shaft portion of lesser diameter. The pur pose of channelling or grooving each grinding body is that it may engage an annular guide t which may be supported by screws u extended through the outer grinding ring d. The grinding bodies thus guided will nearly always maintain their true positions, with their axes parallel with theaxis of the machine, but it is obviously impracticable, in a machine of this character, to maintain such close fit between the guide t and the oooperating surfaces of the grinding bodies that the true position of each grinding body shall be maintained invariably under all conditions of operation. Furthermore, not only will the guide 2f be or become narrower than the groove or channel in each grinding body,

Y which is between the two forces.

upper member being represented by 01. like manner the lever but, as the guiding ring constitutes the vertical support for the grinding bodies, the lower face of the upper portion 6 of each grinding body will rest at all times upon the upper face of the guiding ring, and the upper face of the lower member 6 will, in a corresponding degree fall away from the lower face of the guiding ring. These conditions are obviously true whether a single guiding ring be employed or an inner guiding ring t as well as the outer guiding ring t, as indicated in the drawing. The forces which act upon each grinding body to effect it rolling against the outer grinding ring are two, viz, one force K which acts tangentially along the periphery of the upper part c of the grinding body, and a corresponding force K which acts tangentially along the periphery of the-lower part c of the grinding body and each of such forces may be regarded as acting 1n the central plane of each member. Each such force, if acting alone,

would tend to tilt the grinding body about.

the plane of support of the grinding body The upper force, in the arrangement represented diagrammatically in Figure 3, would tend to tilt the grinding body in a clockwise direction, while the lower force would tend to tilt the grinding body in theopposite direction. If the two forces were equally balanced, therefore, there would be no tendency, in operation, to tilt the grinding body from its true position. However, the lever arms through which each force acts with a tendency to tilt the body, that i the distances from the central plane of each member of the body to the intermediate plane of support of the body, are unequal because of the practically necessary looseness of fit of the guiding ring 1; in the groove or channel of each grinding body. The distance or lever arm through which the upper force acts may be represented as {46, the width, in a vertical direction, of the In arm or distance through which the lower force acts may be represented by y-l-z, 3 being the width of the face of the lower member and 2 being the width of the space between the proximate faces of the two members. For equilibrium in operation the product of the upper force multiplied by-the length of its lever arm must equal the product of the lower force multiplied by its lever arm. Expressed in an algebraic equationthis would be -iy+ The forces K and K may be considered to be proportional to 00 and 3 respectively and a: and 3 may therefore be substituted for K and K in the foregoing equation, giving,

l- 1+ This becomes a a/ ew, or

It will be obvious, therefore, that in order to maintain each grinding body in true position, the two members of the grinding bodv I must be unequal in width, and that the value of z in the foregoing equation being determined by constructive requirements, and the width of one member of the grinding body being determined arbitrarily, the width of By the improved devices described above it becomes possible to secure the broader grinding surface permitted by the use of the cylindrical grinding bodies without subjecting the machine to the difliculties in operation which would be incident to any tilting of the grinding bodies out of their true positions with their axes parallel with the axis of the machine. In other respects the machine is substantially as described in the application referred to. Below the lower disk I) is a disk j which is extended nearly to the casing and is provided on its under side with fan blades Z, so that air admitted through the openings at around the lower bearing 0, is forced upwardly through 5 the annular space 7' and the narrow spaces (Z between the outer face of the outer grinding ring d and the casing k. The material to be ground is introduced through a pipe 7) which extends downwardly through the upper blade 70'' of the casing A: through a larger opening 9, and surrounds loosely the hub of the upper plate 6. The material to be ground is introduced through the pipep, falls on the upper face of the diS b, and by centrifugal action is thrown off the edge of this disk into the space in which the grinding bodies 6 roll, the outer grinding ring d being extended above the plane of the disk I) to prevent the material from passing beyond the outer grinding ring. As the material passes downward in the space between the grinding rings, it is subjected to the action of the grinding bodies and, falling upon the disk j, is thrown ,ofi at lUU ' its edge into the upwardly moving current of air, by which it is carried up through the spaces (Z and is discharged into the space above the upper disk. The upwardly moving air loses some of its lifting force in the enlarged chamber above the disk 6 and only the finely ground material passes on with the air through the annular channel 9, the coarser material falling back into the space between the grinding rings or upon the upper disk Z) and so being subjected again to the grinding action of the machine. This operation is continued until all of the material has been reduced to such degree of fineness that it will be carried out of the machine by the air current. It will be understood that in the present case as in the former case the inner, sectional grinding ring is forced outward by centrifugal action against the grinding bodies and presses the grinding bodies outward against the outer grinding ring and that "the sections of the inner grinding ring are free to yield inwardly either as a whole or at each end, thereby reducing the shocks as the grinding bodies pass from one to another, but are held from movement in a vertical direction. It will further be seen that the grinding bodies are supported and guided by the guiding rail, or held from angular displacement by the guiding rail and finally are prevented from tilting which might otherwise be permitted by reason of the looseness of the guiding rail.

It will be understood that various changes in details of construction and arrangement can be made to suit different conditions of use and that the invention is not limited to the precise construction shown and described herein except as pointed out in the claims.

I claim as my invention:

1. In a grinding machine, the combination of a grinding ring, cylindrical grinding bodies co-operating with the grinding ring and channeled circumferentially between their ends, and an annular guide engaging the circumferential channels of the grinding bodies to maintain them with their axes substantially, in fixed relation with the axis of the grinding machine.

2. In a grinding machine, the combination of an outer grinding ring, an inner sectional grinding ring, cylindrical grinding bodies interposed between the grinding rings, means to urge the sections of the inner grinding ring outwardly against the grinding bodies, and means to maintain the rinding bodies with their axes substantia lly in fixed relation with the axis of the grinding rings.

8. In a grinding machine, the combina tion of an outer grinding ring, an inner sectional grinding ring,'circumferentially channeled, cylindrical grinding bodies interposed between the grinding rings, means to urge the sections of the inner grinding ring outwardly against the grinding bodies, and an annular guide engaging the circumferential channels of the grinding bodies to maintain them with their axes substantially in fixed relation with the axis of the grinding rings.

4. In a grinding machine, the combination of an outer grinding ring, an inner sectional grinding ring, grinding bodies interposed between the grinding rings, a carrier for each ring section, and an S-shaped spring secured at one end to the carrier and supporting at its other end the corresponding ring section.

5. In a grinding machine, the combination of an outer grinding ring, an inner sectional grinding ring, grinding bodies interposed between the grinding rings, supporting means, a carrier for each ring section radially movable on the supporting means, and an S-shaped spring secured at one end to the carrier and supporting at its other end the corresponding ring section.

6. In a grinding machine the combina tion of a grinding ring, cylindrical grinding bodies co-operating with the grinding ring, each of such-grinding bodies being channeled circumferentially between its ends to form upper and lower members, and an annular guide engaging the channels of the grinding bodies, the widths of the two meme bers of each grinding body being unequal and inversely proportioned to the distance of the central plane of each from the plane of contact of the upper member with the annular guide.

This specification signed this 9th day of February, A. D. 1921.

KRISTIAN MIDDELBOE. 

